1. Field of the Invention
The present invention generally relates to bone fixation systems. An embodiment of the invention relates to an extender plate that attaches to a previously inserted bone plate. The extender plate may allow for stabilization of an additional vertebral level or levels.
2. Description of Related Art
An intervertebral disc may be subject to degeneration caused by trauma, disease, and/or aging. The intervertebral disc that becomes degenerated may have to be partially or fully removed from a spinal column. Partial or full removal of the intervertebral disc may destabilize the spinal column. Destabilization of a spinal column may result in alteration of a natural separation distance between adjacent vertebrae. Maintaining the natural separation between vertebrae helps to prevent pressure from being applied to nerves that pass between vertebral bodies. Excessive pressure applied to the nerves may cause pain and/or nerve damage. During a spinal fixation procedure, a spinal implant may be inserted in a space created by the removal or partial removal of an intervertebral disc between adjacent vertebrae. The spinal implant may maintain the height of the spine and restore stability to the spine. Intervertebral bone growth may fuse the spinal implant to adjacent vertebrae.
A spinal implant may be inserted during a spinal fixation procedure using an anterior, lateral, or posterior spinal approach. In some situations, an anterior approach may result in an easier approach, less muscle and tissue damage, and/or less bone removal than other approaches.
A discectomy may be performed to remove or partially remove a defective or damaged intervertebral disc. The discectomy creates a disc space for a spinal implant. After a discectomy, the spinal implant may be inserted into the disc space. One or more spinal implants may be inserted between a pair of vertebrae. Spinal implants may be inserted into disc spaces prepared at multiple vertebral levels during a spinal fusion procedure.
A spinal plate may be coupled to vertebrae after insertion of the spinal implant. The spinal plate may stabilize the vertebrae and inhibit backout of the spinal implant from between vertebrae. A spinal plate may share a compressive load applied to the spinal implant or spinal implants inserted between vertebrae. Fasteners (e.g., bone screws) may be used to fasten the spinal plate to vertebrae. Spinal plates may be used to stabilize sections of cervical spine and/or sections of lumbar spine.
Fastening systems used to attach a spinal plate to vertebrae may attach the spinal plate to the vertebrae without allowing fasteners of the fastening systems to backout from the vertebrae. A fastening system may include a fastener and a ring. The ring may be positioned between the plate and the fastener. Backout of fasteners from the spinal plate may be inhibited without allowing the fasteners or the rings to immovably fix to the spinal plate. The ability to fasten the plate to the vertebrae without the fastening system immovably fixing to the plate may allow the position of the plate relative to the screws to change to accommodate for settling of the vertebrae. U.S. Pat. No. 6,331,179 to Freid et al. and U.S. Pat. No. 6,454,769 to Wagner et al., both of which are incorporated by reference as if fully set forth herein, describe bone plate systems.